A thermodynamic theory of the Grüneisen ratio at extreme conditions: MgO as an example     

Orson L. Anderson  Hitoshi Oda  Anastasia Chopelas  Donald G. Isaak 《Physics and Chemistry of Minerals》1993,19(6):369-380

The Grüneisen ratio, γ, is defined as γy=αK _TV/C_v. The volume dependence of γ(V) is solved for a wide range in temperature. The volume dependence of αK _T is solved from the identity (? ln(αK _T)/? ln V)T ≡ δ _T-K′. α is the thermal expansivity; K _T is the bulk modulus; C _V is specific heat; and δ _Tand K′ are dimensionless thermoelastic constants. The approach is to find values of δ _T and K′, each as functions of T and V. We also solve for q=(? ln γ/? ln V) where q=δ _T -K′+ 1-(? ln C _V/? ln V)T. Calculations are taken down to a compression of 0.6, thus covering all possible values pertaining to the earth's mantle, q=? ln γ/? ln V; δ _T=? ln α/? ln V; and K′= (?K _T/?P)T. New experimental information related to the volume dependence of δ _T, q, K′ and C _V was used. For MgO, as the compression, η=V/V ₀, drops from 1.0 to 0.7 at 2000 K, the results show that q drops from 1.2 to about 0.8; δ _T drops from 5.0 to 3.2; δ _T becomes slightly less than K′; ? ln C _V/? In V→0; and γ drops from 1.5 to about 1. These observations are all in accord with recent laboratory data, seismic observations, and theoretical results.  相似文献   

The source process of the 2001 July 26 Skyros Island (Greece) earthquake     

Zafeiria Roumelioti  Anastasia Kiratzi  Douglas Dreger 《Geophysical Journal International》2004,156(3):541-548

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Pressure-induced phase transition in Mg0.8Fe0.2O ferropericlase     

Innokenty Kantor  Leonid Dubrovinsky  Catherine McCammon  Anastasia Kantor  Sakura Pascarelli  Giuliana Aquilanti  Wilson Crichton  Maurizio Mattesini  Rajeev Ahuja  Jailton Almeida  Vadim Urusov 《Physics and Chemistry of Minerals》2006,33(1):35-44

Combined X-ray powder diffraction, Mössbauer, and XANES spectroscopy in situ experiments revealed the transformation of cubic (Mg_0.8Fe_0.2)O ferropericlase to a rhombohedrally distorted phase at 35(1) GPa and room temperature. The Mössbauer spectroscopy results show that the rhombohedral distortion does not involve magnetic ordering. Combined with data from the literature, our results imply that the cubic to rhombodedral transition occurs in (Mg,Fe)O under conditions of non-hydrostatic stress over a wide range of composition (0.2≤x _Fe≤1).  相似文献   

S-wave spectral analysis of the 1995 Kozani-Grevena (NW Greece) aftershock sequence     

Zafeiria Roumelioti  Anastasia Kiratzi  Nikos Theodoulidis  Christos Papaioannou 《Journal of Seismology》2002,6(2):219-236

S-wave spectral analysis is applied to 174 strong motion accelerationrecords to obtain the source parameters of 27 aftershocks(3.1 M_L 4.3) of the May 13, 1995, M_w 6.6,Kozani-Grevena (NW Greece) earthquake. The data are derived from atemporary network, of three-component digital accelerographs, deployedwithin the strongly affected area some days after the mainshock occurrence.Site effects were evident in the strong motion records at 3 out of the 4stations used, and a correction was applied to account for theoverestimation of seismic moment due to amplification of thelow-frequency part of the spectrum. The data from this analysis arecomplimented with previously obtained source parameters for earthquakesin Greece, in order to study the applicability of the empirical scalingrelations used so far, towards smaller magnitudes. In general, a goodcorrelation was observed in most cases, validating the use of empiricalrelations that are applicable to the Aegean area. Empirical relations aredetermined between seismic moment and seismic slip, as well as, betweenseismic moment and stress drop, applicable to small magnitude earthquakes(M_L < 4.3). Stress drop values were found to be relatively small,ranging from 2 to 41 bars, indicative of inter-plate environments. Thevalues of f_c and of f_max were found in good agreement withrelations based on observations from larger worldwide earthquakes.  相似文献   

Environments of the Russian Plain during the Middle Valdai Briansk Interstade (33,000–24,000 yr B.P.) Indicated by Fossil Mammals and Plants     

Anastasia K. Markova  Alexandra N. Simakova  Andrei Yu. Puzachenko  Lev M. Kitaev 《Quaternary Research》2002,57(3):391

Abundant mammal (45 localities) and plant (52 sections) fossil data collected from the Russian Plain deposits of the Middle Valdai Briansk Interstade indicate a period of noticeable warming. These materials were jointly analyzed. The data were organized in the database software PARADOX and then moved to the GIS program ARC/INFO. Mathematical methods as well as traditional research methods were used for the analysis. The reconstructed biogeographical provinces illustrate the specific environmental and climatic conditions of the Briansk Interstade. Analogues of modern natural zones did not exist at this time on the Russian Plain. The Briansk landscapes reflect the moderate-cool climate of this period, when the majority of northern subarctic plant and mammal species extended their ranges considerably to the south to the Central Russian Plain. At the same time, steppe species penetrated farther north and west. This combination shows that the continuous forest zone was destroyed during the Briansk Inter-stade. Five biogeographical provinces have been reconstructed from the north to the south for the Russian Plain during the Briansk warming on the basis of joint analysis of mammalian and botanical data.  相似文献   

Geomorphology of subglacial volcanoes in the Azas Plateau, the Tuva Republic, Russia     

Goro Komatsu  Sergei G. Arzhannikov  Anastasia V. Arzhannikova  Kirill Ershov 《Geomorphology》2007,88(3-4):312-328

The Azas Plateau volcanic field is located in the Tuva Republic of the Russian Federation. The compositions of the Azas Plateau volcanics include low-viscosity trachybasalt and basanite. Volcanic edifices of Middle-Late Pleistocene age are widely distributed in the southeastern part of the volcanic field. There are subglacial volcanoes among the volcanic edifices, and their formation coincided with extensive ancient glaciations in the region. The dominant subglacial volcanoes in the area are tuyas. The general shapes of the tuyas (flat-tops with steep sides) are due to eruptions into meltwater lakes and confinement of ice walls, and effusive subaerial eruptions of basaltic lavas. There are also non-flat-topped subglacial volcanoes and at least one subaerial volcanic edifice in the area. Degradation appears to have modified the primary shapes of the tuya edifices, and such processes seem to include failures of over-steepened slopes, gully formation due to stream runoff and debris flows, cirque/valley glaciation, and modification by rock glaciers. The estimated thicknesses of the ice sheets covering the subglacial volcanoes during their eruptions range 300–600 m on average.  相似文献   

Late Pleistocene Eifel eruptions: insights from clinopyroxene and glass geochemistry of tephra layers from Eifel Laminated Sediment Archive sediment cores     

Michael W. Förster  Anastasia Zemlitskaya  Laura M. Otter  Stephan Buhre  Frank Sirocko 《第四纪科学杂志》2020,35(1-2):186-198

The Eifel Laminated Sediment Archive (ELSA), which comprises several cores from maar lakes, includes numerous tephra layers spanning the last 140 000 years. The sediment cores are dated by ¹⁴C and thermoluminescence as well as tuned to Greenland stadial–interstadial successions. Within the last glacial cycle, the Eifel Volcanic Fields are source to several widespread tephra layers, namely the Laacher See, Eltville, Rambach and Rocourt Tephra. However, a corresponding source volcano was so far only identified for the Laacher See Tephra. In this study we use glass and clinopyroxene geochemistry to link the remaining tephra layers to possible eruption centers within the West and East Eifel Volcanic Fields: while we demonstrate that the Eltville Tephra originated from an earlier eruption of the Laacher See Volcano at 24 300 a bp from within the East Eifel Volcanic Field, the Rambach and Rocourt Tephras are sourced from the West Eifel Volcanic Field and erupted from Wartgesberg at 27 900 a bp and Pulvermaar at 75 000 a bp , respectively. Phases of volcanic activity peaked at 10 000–30 000 and 60 000–80 000 a bp and were thus erupted around the temperature minima of the last glacial cycle. The longest phase of dormancy between individual vents was around 30 000 years long, within the last interglacial.  相似文献   

Temperature and heat flux changes at the base of Laurentide ice sheet inferred from geothermal data (evidence from province of Alberta,Canada)     

Demezhko  Dmitry  Gornostaeva  Anastasia  Majorowicz  Jacek  Šafanda  Jan 《International Journal of Earth Sciences》2018,107(1):113-121

International Journal of Earth Sciences - Using a previously published temperature log of the 2363-m-deep borehole Hunt well (Alberta, Canada) and the results of its previous interpretation, the...  相似文献   

Chemical Composition of Some Saline Lakes in the Tuva Region(Russia)   总被引：1，自引：0，他引：1  

Yulia KOPYLOVA  Natalia GUSEVA  Choyganmaa OYDUP  Anastasia SHESTAKOVA 《《地质学报》英文版》2014,88(Z1):82-83

正1 Introduction Salt lakes are very interesting natural objects which can be found in different places in the world.Russia is not an exception.Climate conditions are various in Russia,but the climate is not very hot.In Russia there are a lot of places where salt lakes are spread.One of them is the Tuva region where lakes with different compositions are  相似文献   

Modelling carbon dynamics from urban land conversion: fundamental model of city in relation to a local carbon cycle   总被引：2，自引：0，他引：2  

Anastasia Svirejeva-Hopkins  Hans-Joachim Schellnhuber 《Carbon balance and management》2006,1(1):8-9

Background  

The main task is to estimate the qualitative and quantitative contribution of urban territories and precisely of the process of urbanization to the Global Carbon Cycle (GCC). Note that, on the contrary to many investigations that have considered direct anthropogenic emission of CO₂(urbanized territories produce ca. 96–98% of it), we are interested in more subtle, and up until the present time, weaker processes associated with the conversion of the surrounding natural ecosystems and landscapes into urban lands. Such conversion inevitably takes place when cities are sprawling and additional "natural" lands are becoming "urbanized".  相似文献